The main advantage of more people is a deepening of the market and the
division of labor. More people means more ideas and more specialization.
But the law of diminishing marginal productivity suggests that each
additional unit of labor and of human capital is of less value.
Furthermore, in a world of 7 billion people we are going to get roughly
as many outlier geniuses as we do in a world of 9, 10, or 15 billion.

I'm frankly puzzled. Why wouldn't outlier geniuses be exactly proportional to total population? Furthermore, a lot of innovation - probably most - comes not from geniuses, but from tons of smaller contributions of lots of lesser minds.

In fact, there's a good reason to think that innovation will rise at more than a proportional rate: Population increases not only the supply of innovation (more people to create ideas) but the demand for innovation (more consumers around to pay for ideas). As I've said before:

If, like the Professor, you have only seven potential customers counting yourself, most innovations won't pay. Suppose the Professor could spend a year of his life working on an idea worth $1 per person. As long as he's stuck on the island, he'll be working for $7 a year. He'd be better off picking coconuts. If the Professor could escape the island and bring his idea to a world market of 7 billion customers, though, it would amply repay a lifetime of research.

Sorens continues:

Along with diminishing marginal benefits of people, there are rising
marginal costs. The human footprint on the natural environment increases
with population, and intrudes ever more into ever scarcer (and more
socially valuable) undisturbed habitats.

One way to limit environmental externalities is to (voluntarily or involuntarily) limit population. But environmental economics teaches us far cheaper and more humane alternatives: taxes and tradeable permits. Questioning a person's existence because he drives a car is severe overkill.

People don't like being crowded. Part of the reason why people move to
suburbs and exurbs is not just high crime and costs in central cities,
but distance from other people. Where do people go to "get away"?
Generally rural and wilderness areas.

Some people don't like being crowded. But most seem to love it. Real estate prices are much higher in densely-populated areas, and the reason is simple: People prefer (all the benefits of population + all the drawbacks of population) to splendid isolation. If Jason were right, real estate would actually be cheaper in big cities. It's not.

More people in a country mean more agency problems
with the government. The people find it more difficult to constrain
their rulers when their rulers don't pay attention to individual voices,
or even small clusters of people. As a country of over 300 million, the
U.S. would face severe agency problems were it not for the federal
system -- and even so, agency problems are significant.

There may be something to this, but it's not a big deal. If it were, real estate prices would be noticeably lower in high-population countries and political subdivisions. And in a world of largely closed borders, there's an obvious benefit of large polities: They create big free-trade and free-migration zones, with all the attendant wonders.

More people will mean more infectious disease.
It is a basic principle of ecology that a higher population of a
species encourages greater parasitism on that species. As human
populations have increased, so have human diseases.

This is probably true all else equal. But mankind has gotten much healthier during the population explosion of the last two centuries, and there's a simple explanation: Larger populations lead to more innovation, including more innovation in medicine and sanitation.

Bottom line: Jason should stop doubting the case for natalism. Yes, population has some drawbacks. It's conceivable that one day these drawbacks will exceed the benefits. But we have a very long way to go before we reach that point. Until then, the more the merrier.

Good post with all the right responses. Basically, every one of Sorens's points is wrong. In a well-connected free market economy where increased value comes from trade, per capita income and wealth grows proportionally with population. As you point out with your island example, more trading available partners means more wealth per person.

This notion is not just a theoretical supposition either. It's strongly supported by historical economic data (e.g. Maddison, deLong). According to Maddison's data, from 1800 -2000 world per capita GDP in constant dollars grew at a rate 1.1 times the rate of population growth, exactly as expected from the simplest model.

It is true, of course, that the human footprint increases proportionally with population, but the cost of mitigation per capita decreases, which is why cities today are cleaner and safer and people are healthier than ever before.

Even things like infectious diseases can't increase faster than the human interaction (trade) will allow, which means the cost of mitigation is at most constant with respect to per capita GDP and probably decreasing.

The bottom line is that more people is an unqualified good in the long run and will remain so for the foreseeable distant future. Natalism reigns supreme!

Why wouldn't outlier geniuses be exactly proportional to total population? Furthermore, a lot of innovation - probably most - comes not from geniuses, but from tons of smaller contributions of lots of lesser minds.

The claim is even more wrong than this. Innovation does not arise from one person sealed in a room. Innovation begets innovation and therefore rises quadratically with the population available to innovate.

> Some people don't like being crowded. But most
> seem to love it. Real estate prices are much
> higher in densely-populated areas, and the reason
> is simple: People prefer (all the benefits of
> population + all the drawbacks of population) to
> splendid isolation. If Jason were right, real
> estate would actually be cheaper in big cities.
> It's not.

The right thing to do is to add up the real estate value of big cities and the real estate value of alternatives like suburbs and rural areas and compare that, rather than prices.

What you're doing is like saying "Look, a tiny flat in Hong Kong sells for $3M, so most people must prefer living in a tiny flat in Hong Kong," which is of course absurd. You couldn't make most people live there if you gave it to them for free.

I think if you performed the computation I proposed you'd find, at least in the United States, but maybe in the world, that suburbs completely dominate.

There's a further argument for just counting noses rather than dollars.

Put another way, the price indicates how much someone's desire is for that one thing. The price times the volume indicates how much desire there is for that whole set of things. Prices might be lower in Brookline and Belmont than Back Bay, but there's a heckuva lot more people living in places like Brookline and Belmont.

On the margin people in the United States must prefer to live in cities because most of the incentives push people to live in suburbs: zoning laws that prevent higher densities in cities and failure to price congestion of city street use for transit or parking.

I've shocked no one has explicitly brought up Network Affects and Metcalfe's law yet. Innovation/technology gets an exponential boost in the size of benefits from network effects and the more people, the larger the network.

If anything, I would expect the rate of geniuses and lower level contributions to increase exponentially with population increases because of the impact of the additional available knowledge for those doing the innovation to build upon. I'm sure there are some knowledge acquisition issues to go along with that, but having too many giants to stand on the shoulders of isn't exactly something to deride.

Suburbs are part of the "city".
urban area (500 people/sqmi)includes most suburbs as it is any area denser than ~1/acre
even if you want to quibble about whether it includes most suburbs

urbanized area population ~80% of U.S. population
urbanized area land ~2.6% of total U.S. land area

=> "Some people don't like being crowded. But most
seem to love it." We know this because we have plenty of room to spread out if we didn't want to be near other people.

P.S. even non rural population that represents about 20% of the population is on only ~4.2% of the land.
P.P.S. The price of land is high closer to city centers because lots of people want to live close to city centers, relative to the supply of apartments. That high land value is what leads to smaller apartments/lots. If someone valued living in that apartment for $3M and no one else wanted to live there he could pay $0 and capture that whole difference between his valuation and the market price.

America's population in 1950 was about 150 million. India's population today is about 1.2 billion. Innovation is a function of more variables than population. And its certainly not linear with population.

Adding more psychopaths to the population doesn't make the world a better place. Neither does adding more depressive people, low-IQ people, and so on.

Save the money that would be spent on those additional children, and spend it on better ways to select desirable traits instead. Robert Graham had the right idea, and it can certainly be improved and used for other predictors of a good life with positive externalities.

The populations of individual countries don't matter much because of international trade. What matters is the size of the entire trading network, which in this case is the entire world population. To put it simply, India's 1.2 billion help to make Americans rich.

Regarding innovation, certainly it depends on more than population, but it doesn't change the fundamental reality that WEALTH from innovation depends mostly on how many trades one can make. Innovation does one of two things: it either makes available new areas of specialization (increasing the value per trade) or it increases the pace at which trades can occur. Either way, growth in the population of trading partners is the primary driver of wealth creation.

There is no assumption that more people is better. It's an INFERENCE based on economic theory and data.

Also, you say "Adding more psychopaths to the population doesn't make the world a better place. Neither does adding more depressive people, low-IQ people, and so on."

ARE YOU SURE? I know you think your statement is obvious, but in fact it's not. Psychopaths and imbeciles still buy food and rent apartments, do they not? They still act as trading partners, don't they? If a psychopath buys food from you but does not interact with you in any other way, aren't you better off? Who's to say that even the psychopath doesn't provide a net benefit to society? If nothing else, this diversity of human intelligence and personality helps drive waelth creation through comparative advantage, in which the least among us still take on tasks that free up the best and brightest to do what they do best.

Besides, from an evolutionary point of view, if having everyone be much smarter is really the big advantage you think it is, we would ALREADY be much smarter. Eugenics is fundamentally flawed, if only because it fails to recognize the importance of diversity in all facets of life for the creation of wealth.

I agree with the general point that diversity is good, but this doesn't imply all diversity is good. For instance, many genetic disorders are clearly a net negative, even if they can have occasional upsides or increase diversity.

While sociopaths may fill some professional niches that aren't attractive to people with more empathy, thus adding some value to society, it's hard to see them as a social net gain, as a fraction of them manages to do massive individual harm. And callous or stupid people can be rent-seekers, voters or criminals.

Furthermore, all additional lives start with a negative: Children do not consent to being born, they will endure years of non-autonomy, and suffering is a real cost to every born individual, which is mandatory. Natalists always brush this away as if it weren't a factor to consider.

But let me more cautiously state that, on the margin, if you can choose to have more children or else to have better children, having better children can easily be the better choice. Selecting for quality costs money (not just eugenics, also other forms of health and education).

Besides, from an evolutionary point of view, if having everyone be much smarter is really the big advantage you think it is, we would ALREADY be much smarter.

But my claim wasn't about the workings of natural selection but the possible benefit of artificial selection, e.g. through reproductive technology.

> mankind has gotten much healthier during the population explosion of the last two centuries, and there's a simple explanation: Larger populations lead to more innovation, including more innovation in medicine and sanitation.

The populations of individual countries matters when we are testing the hypothesis 'more people ~ more X', and the countries are our treatment groups. After all, you have to group the data somehow, and using The Whole Planet at different times is like bringing reading glasses to a microscope fight, especially when we are talking about the last two centuries, where we have plenty of data/information to get a better picture. Also, because of serial correlation, looking only at total pop over time could lead to spurious inference: namely, wealth/innovation leads to more population, not the other way around. Yes there are uncontrolled variables, like trade, but we cant make assignments so what are you gonna do?

Anyway, taking a very cursory look (in a panel data manner) over the last couple of centuries (cause they are the most interesting), its pretty obvious that the most innovative and wealthy (per capita, cause thats what matters) places tend not to be the least populated, or the most populated. Now maybe there is a vector of omitted variables that explain the pattern, but it is consistent with the boundary conditions (i.e. Population = 0, Population = Malthusian limit)

Real estate prices contain information on many things. Only part of the price is preference (or lack of) for "wide open spaces". Real estate prices can be higher in cities for other reasons. The obvious: more jobs are in cities. Same point for "real estate prices would be lower in high population countries".

The conclusion that the price is higher so it must be x that makes the price higher is flawed. Figuring out why prices are high for goods with some characteristic and low for goods with other characteristics is a difficult problem.

awp, your definitional quibble is silly. There's an obvious difference between single-family houses on one acre lots and high-rise apartments.

In any event, my point wasn't that Americans prefer modest densities (suburban sprawl) over both high densities and low densities although that's pretty clearly true, it was that Bryan's method of measuring what people "want" is wrong. You need to look at the depth of the market, the quantity demanded, as well as the price to get the right answer.

"But let me more cautiously state that, on the margin, if you can choose to have more children or else to have better children, having better children can easily be the better choice."

Rob,

I agree that having a smaller number of "better" children could be of more benefit (both to the parents and to society) than having more "not better" children, but I think you underestimate how difficult it is for improvements in quality to outweigh increases in sheer numbers.

Let's look at economics alone. Let's say the average person creates $4 million in net value in their lifetime. Every child you have contributes $4 million. Now you say, let's forego having another child so we can provide a higher-quality upbringing for the children we already have. What, exactly, can you do in improved quality that will add $4 million in value to what your children produce? It's virtually impossible. The marginal value of adding one more child far outweighs any loss in quality.

But this argument is not unique to economic matters. Regardless of what one wants to maximize--quality of life, happiness, human knowledge, etc.--having more people is usually the easier way to achieve maximization than improvements in quality. Ideally, of course, BOTH should work together, but it's a myth that there's a net marginal benefit to having fewer people.

With regard to diversity, too broad a range is chaotic and counterproductive; too small a range is sterile. But it's not obvious that sociopaths and low-IQers provide too much diversity. Again, it's hard for quality issues to outweigh pure numbers. For example, how many people do sociopaths kill in a human lifetime? Let's say millions. That's still a small number compared to the 100 million sociopaths (just to make up a number) in the world who are reasonably productive. And it's not clear at all that an attempt to eliminate sociopathic tendencies would be a net gain.

Finally, the whole pre-birth consent issue is a red herring. Children cannot brought into the world against their will because they HAVE no will before they are born. In this context, consent is meaningless. Suffering is a real cost, yes. I don't no anyone who ignores or denies it. But for nearly everyone, suffering is a small cost compared with the overall advantages of being alive. It is better to have lived and lost, than never to have lived at all. This is one of Bryan's key points, and it seems rather obvious.

"The populations of individual countries matters when we are testing the hypothesis 'more people ~ more X', and the countries are our treatment groups."

S,

Whether country populations matter depends on what X is. In the case of wealth, what matters is the number of trading partners and the value per trade. If trading beyond one's country is common and well-integrated into the national economy, then the country's population matters a lot less. For a country with closed borders, the internal population would matter much more.

For testing the effects of population on wealth creation, growth over time is exactly the right test. The reason is that a free-market, capitalist model makes very specific predictions about how growth in the trading population relates to growth in wealth. Specifically, network effects (happy, Thomas Sewell?) ensure that per capita wealth should grow a little bit faster than population from the combined effects of network and technological innovation. This is exactly what we see from 1800 on. Prior to 1800, the growth in per capita wealth was

Finally, in this case there is on danger of drawing spurious inferences because BOTH directions are expected to be causal--more trading population leads to more wealth/innovation but more wealth/innovation leads to more population growth. Over the last two centuries, the two have worked together in a giant feedback loop to greatly advance human prosperity.

On this we just dont agree/are talking past each other. I think it is valid, perhaps necessary to look at cross country (or SOME cross sectional)comparisons, you seem to disagree

For testing the effects of population on wealth creation, growth over time is exactly the right test

Well, yeah. The point is that different cross sections (over time) constitute different "experiments" to test the hypo. And the most populated do not seem to be the most innovative, or wealthy, which would seem to matter.

Finally, in this case there is on danger of drawing spurious inferences because BOTH directions

On this we agree, and I was unclear. But again, this just supports looking at cross section at different points in time as well.

more trading population leads to more wealth/innovation but more wealth/innovation leads to more population growth

Yes, but more population does not always equal more "trading population". Boundary conditions matter, people at the malthusian limit dont have much to trade.

Over the last two centuries, the two have worked together in a giant feedback loop to greatly advance human prosperity.

"Besides, from an evolutionary point of view, if having everyone be much smarter is really the big advantage you think it is, we would ALREADY be much smarter."

No.

Evolution selects primarily for individual reproductive success, not for species benefit. It could be that raising the IQ of someone by 10 points would make humanity better off but result in his producing fewer children (complications of extended reproductive success ignored for simplicity), in which case additional IQ will be selected against, not for.

The discussion of absolute numbers has the implicit assumption of equal probabilities of a contribution to the whole by all sub-groups. This assumption is false. Just look at the number of Nobel's in the culturally Jewish community vs the Muslim community. The probabilities of making a contribution to humanity are a thousand times higher, whereas population numbers only vary a small factor (the difference between 3 billion and 15 billion people is only a factor of 5, with a huge impacts on resources with little benefit to humanity if the extra 10 billion are from low-contributing cultures).

Many of the cultures around the world use resources linearly with the population numbers, while not contributing anything to humanity beyond tribalism. With the marginal utility of population combined with increased environmental stress created by absolute numbers, increased populations, especially among less productive cultures, will actually decrease human progress.

It is magical thinking to assume that ALL sub-cultures will be able to change and progress and contribute to the world when a more parasitic life style is very viable. Does anyone really believe that Saudi Arabia throwing trillions of dollar trying to get its population into the 21st century will succeed in making anywhere near the contributions to humanity that we see coming from small countries like Singapore. As long as the majority of Saudi Ph.D.'s are in theology they will continue to live off their resources and make no positive contributions to humanity.

But for nearly everyone, suffering is a small cost compared with the overall advantages of being alive.

I'd be interested in the evidence for this claim.

I'd also be interested in evidence supporting that, even if it is true, there isn't a remaining minority whose suffering is disproportionately intense or prolonged, or that a "quality over quantity" approach to reproduction can't affect this minority meaningfully.

The evidence is that we rarely hear anyone say "I wish I were dead." When we DO hear that, we think something is terribly wrong. If it were common for suffering to make life not worth living, wouldn't our natural response be "That's life!" The other evidence is, of course, as Bryan said, namely that few people actually try to kill themselves. The final point is that suffering of a given magnitude is always potentially avoidable, which means that its cost can almost always be reduced to a small value. I can honestly say that I and my family have suffered very little in our lives, so it is clearly not an INTRINSIC part of life. And if it's not intrinsic or immutable, you can't argue that bringing someone into the world inflicts suffering on them.

The marginal value of adding one more child far outweighs any loss in quality.

Well, if that were true, you could add a thousand chimps and hope it helps the economy. Clearly not true. Assuming some intellectual tasks can only be performed by very talented people, the marginal value of adding 3 of them can easily be higher than the marginal value of adding 50 people whose intellectual ability only extends to burger-flipping level. Especially because we will soon have burger-flipping robots. (*)

Let's consider the cost of suicidally depressed people. Clearly, helping suicidal people survive and get better is economically good because it keeps more people in the population than letting them die? The argument is sometimes used in defense for coercive suicide prevention and euthanasia prohibition.

But the empirical answer seems to be that completed suicides actually save a lot of money. If death at this stage is cheaper, what's the savings potential of not paying all the upbringing and education costs of depressive people in the first place, by, say, selecting against genes predicting higher probabilities of depression?

(*) Of course, when robots become geniuses themselves, we puny humans will have very different problems to worry about.

@S

Boundary conditions matter, people at the malthusian limit dont have much to trade.

Technically, they can sell intangibles, such as attention or status even if their productive labor is worthless and they have no capital. People could hire human servants and sycophants at subsistence wages as status items. But in a morally egalitarian culture, desire to do so is actually low status ("exploitation").

This is true, of course, but I would argue that the characteristics that lead to biological reproductive success are similar to the ones that lead to human productive success. How can it be otherwise, since our biological inheritance (produced by evolution) is all we have available to drive other forms of production. Is it true that the characteristics of high-IQ people can cause them to have fewer children? Then at some level of IQ, it's also true that they are likely to have trouble achieving success in other areas. What percentage of very high-IQ people never accomplish anything of note. A high one, I'm sure.

More to the point, evolution has already selected out those whose IQ's prevented them from raising children to procreative adulthood (Neanderthals perhaps?). Since human children don't raise themselves very effectively, that already tells us that even low-IQ people are sufficiently aware of the world around them to negotiate it successfully.

"Well, if that were true, you could add a thousand chimps and hope it helps the economy. Clearly not true. Assuming some intellectual tasks can only be performed by very talented people, the marginal value of adding 3 of them can easily be higher than the marginal value of adding 50 people whose intellectual ability only extends to burger-flipping level."

So now chimp = child? I will gladly stipulate that the IQ of a chimp precludes it from functioning effectively in HUMAN society, but I'm not sure what that proves regarding the debate at hand.

More to the point, I think you are misunderstanding "marginal value." This is not a question of adding one more impoverished Somalian child versus adding one more to the Gates family. A given set of potential parents can choose either to have another child or not have one. The marginal value of adding another child compares that net benefit versus the net benefit of that same couple choosing not to. My point is that on average the net benefits of adding a child more than makes up for the losses in child-raising capacity and quality of life for the parents and for society.

Regarding the paper you cite, I haven't read the whole thing but something in the abstract caught my attention. They mention that the main losses accounted for are lost wages and propose to add in the many cost savings of no SS, etc. But the monetary value alone of the suicidal person goes far beyond the wages themselves, since people get paid only a fraction of the value they produce. Given that the net economic benefit of suicide is calculated by them to be only $150,000 per person, it should be clear that the productive value is far above that. In other words, their conclusion depends on ignoring some obvious economic benefits of having the suicidal person continue living. Treating them for depression is certainly cost effective on average, not even counting non-economic considerations.

The marginal value of adding another child compares that net benefit versus the net benefit of that same couple choosing not to. My point is that on average the net benefits of adding a child more than makes up for the losses in child-raising capacity and quality of life for the parents and for society.

But there are opportunity costs nevertheless. A child is a long-term investment; it takes at least 15-20 years before they become economically more productive than they cost, often longer.

Any given couple considering another child could instead use that money differently. If you think better education, reproductive technologies or healthcare for other children aren't sufficiently efficient, other investments still might be. For instance, the couple could invest the same money in technology firms for 15-20 years.

What adds more expected productivity to the economy: Adding a human pizza-deliverer 20 years hence, or investing the money into a firm that invents automated pizza-delivery within 20 years?

Even if your goal is to make more people, you could use the money to affect the future more efficiently, e.g. by funding AI safety research, reduce existential risks, or make future reproduction, upbringing and education cheaper.

I agree. For SOME people there are more productive things one can do with their resources than have another kid. But for many people, effective investment is not an vailable option, or it's too far beyond their experience to seem reasonable. Childrearing is a productive activity available to almost everyone.

Since this seems to be a post with active comments, I'll pose my question here:

Is there pro-adoption economics literature? If so, where? The post's author's book Selfish Reasons to Have More Kids makes adoptive parenting seem to be a nearly-fruitless endeavor.

I know this post was in favor of natalism, but not everyone is physically able to produce children. I'm wondering how those who can't are best able to contribute to society (assuming that smart, successful parents generally don't voluntarily offer their infants for adoption).

I'm wondering how those who can't are best able to contribute to society

What's wrong with earning money and investing it long-term? Assuming we can ride out Moore's Law and improve both algorithmic efficiency and the range of applications of smart algorithms to augment and/or replace human labor. The gains could then be used to alleviate poverty, pay child support, free up people's time, or whatever else you value.

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